There are other greenhouse gases that are not counted in United States or international greenhouse gas inventories:

Water vapor is the most abundant greenhouse gas. Most scientists believe that water vapor produced directly by human activity contributes very little to the amount of water vapor in the atmosphere. Therefore, the U.S. Energy Information Administration (EIA) does not estimate emissions of water vapor. Research conducted by NASA suggests a stronger impact from the indirect human effects on water vapor concentrations in the atmosphere.

Ozone is technically a greenhouse gas because it has an effect on global temperature. However, at higher elevations in the atmosphere (stratosphere), where it occurs naturally, ozone is needed to block harmful ultraviolet light. At lower elevations of the atmosphere (troposphere), ozone is harmful to human health and is a pollutant regulated independently of its warming effects.

Greenhouse gases are transparent to incoming (short-wave) radiation from the sun but block infrared (long-wave) radiation from leaving the earth's atmosphere. This greenhouse effect traps radiation from the sun and warms the planet's surface. As concentrations of these gases increase, more warming occurs than would happen naturally.